KVM: Maintain back mapping from irqchip/pin to gsi

Maintain back mapping from irqchip/pin to gsi to speedup
interrupt acknowledgment notifications.

[avi: build fix on non-x86/ia64]

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
4 files changed